The present invention relates to sealer compositions and more particularly it relates to a solvent-based, clear caulking composition having improved caulking characteristics.
Many types of adhesives, sealants, caulking compositions and the like have been developed heretofore and are discussed at length in the book entitled Sealants by Adolfos Damusis published in 1967 by Reinhold Publishing Company. Many of these compounds are solvent-based ones. See also the Handbook of Adhesives (2nd ed.) chapter entitled "Caulks and Sealants", pages 708-709 wherein the "best" of the solvent based sealants, namely silicones, are discussed. However, as pointed out, even silicone sealants have certain drawbacks. Silicone sealants are translucent/opaque rather than clear, they must be protected from moisture during manufacture and storage, and many silicone sealants on cure either evolve acetic acid (which is corrosive and has an objectionable odor) or they must be specially compounded to avoid that problem.
In addition, solvent-based sealants during gradual release of the solvent undergo a shrinkage of the material and/or sagging of the material (termed "slump" in the trade) prior to its having set-up. This is objectionable in many situations.
For that reason Kutch et al, among others, suggest use of hot melt sealants instead. Thus, in U.S. Pat. No. 4,169,822, Kutch et al disclose solvent-free hot melt caulking compositions which are sufficiently soft or fluid at a temperature above about 150.degree. F. to permit them to be readily applied in use and which harden upon cooling without solvent release. The caulking compositions of Kutch et al contain elastomeric polymers such as butyl rubbers, tackifying resins such as terpene resins, and adhesion promoters which may include ethylene vinyl acetate copolymers. See also U.S. Pat. Nos. 3,991,025; 3,988,276, and 3,392,341 for other references to ethylene vinyl acetate containing hot melt caulking compositions.
Even though hot melt caulking compositions avoid for the most part the problems of slump control, other problems exist. For example, hot melt adhesives must, as mentioned, be applied "hot" (i.e. see the Kutch et al requirement that the hot melt adhesives be applied at temperatures between 150.degree.-375.degree. F.) This requires that special heated applicator equipment be readily available. Other disadvantages to hot melt caulking compositions are potential degradation of the caulk and other problems causing because of its temperature dependence. Because hot melt caulking compositions are organic in nature and are applied at elevated temperatures there is the potential for discoloring, viscosity increases, and skinning since such ingredients may be subject to change in their molten state. Likewise, because the materials must of necessity be temperature dependent care must be taken to ensure proper wetting and subsequent adhesion at all use temperatures.
Accordingly, a solvent-based caulking composition would be desirable if the slump problems could be controlled. In our copending application Ser. No. 699,177 filed Feb. 7, 1985, now U.S. Pat. No. 4,571,410, the disclosure of which is incorporated herein by reference, there is disclosed an improved solvent-based caulking composition which meets that need.
The caulking composition of our copending application contains a blend of highly weather resistant copolymers, resins and plasticizers so as to provide excellent indoor and outdoor caulking performance. The caulking composition applies easily, i.e. it applies "string free" and is easily tooled. The caulking composition can be applied under varying weather conditions including high humidity, moderately cold and warm conditions. Thus, it has many of the advantages of silicone sealants at a fraction of the cost. In addition, its clarity, non-corrosive characteristics and lack of moisture sensitivity make it superior to silicone sealants in many instances.
Still, that composition requires a unique blend of ethylene vinyl acetate copolymers having different vinyl acetate contents. In certain instances where temperature conditions do not vary significantly (i.e. in the tropics) or when the caulk is to be used only during the summer time, such delicate blends are not required. Accordingly, it would be desirable to use a less complex and less expensive caulking composition for those uses and climates.